The following U.S. patents have been found in a U.S. Patent Search and are believed to be generally relevant to the field of the invention:
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When using various media such as video, audio, text and images, a user generally retrieves the media from a storage device or “server” connected via a network to many computers or users. The server downloads the media to the network and transmits it to the user at the user's request.
There are two basic limitations involved in such data retrieval: delay between the time that a user requests the data and the time when the server downloads it to the network, and bandwidth limitations on data throughput and rate of data transmission. The present invention relates to the second limitation.
One example of such a system includes a CD ROM drive and personal computer which may be located at the same site. Another example includes a network connecting Internet servers and users' personal computers. Such networks are installed in order to facilitate convenient data transmission between users and data distribution from the server to the users' computers.
When a user retrieves the media from a storage device or server, typically connected via a network, the aforesaid bandwidth limitations affect the amount of time required to transmit a video frame from the server to the user, and thus limit the video frame rate. Moreover, when dealing with object movies and panoramas the files being transmitted are extremely large, so that overcoming bandwidth limitations is a critical enabling factor, even for high bandwidth networks.
Currently, two methods are employed to overcome bandwidth limitations: The first is to compress the video frame sequence, thereby speeding up transmission time at the cost of additional downstream processing to decompress the frames prior to display. The second is to copy the entire sequence to an intermediate storage device, such as a user's hard disk, to which the user has higher bandwidth access, at the cost of delaying the viewing of the video until the entire sequence has been delivered.
Known network applications involve streaming data from a server to a client computer (hereinafter also referred to as “client”). “Streaming” refers to serial or parallel transmission of digital data between two computers, by transmitting sequences of bit packets. For example, installation executables on a network server stream files to a client computer performing the installation. Servers with large amounts of memory are used to archive digital movies, which are streamed to a client computer for viewing upon demand. Digital video is broadcast from cable stations to subscribers using streaming. Internet browsers, such as Netscape and Microsoft Explorer, are used to stream data from a server on the web to a client. Internet web sites can contain enormous databases, such as phone directories for all of the cities in the U.S., photographs from art galleries and museums around the world, voluminous encyclopedias, and even copies of all patents ever issued by the U.S. Patent & Trademark Office. Clients using the Internet can search these databases and then request the server to download specific information. This request initiates a streaming event.
In view of the multitude of bandwidths present in complex client/server systems today and the large amounts of data necessary to produce compelling audio, video and imaging presentations, there is a pressing demand for scalable data representation of multimedia data, so that it can be delivered for on-line interactive playback in such a form that the transmission rate can accommodate the client bandwidth. The Internet is an example of a complex system where clients with many different bandwidth constraints demand multimedia data from server sites. There are several low bandwidth rates for modem transmission over phone lines, higher rates for frame relay lines, higher rates for ISDN lines, even higher rates for T1 lines, etc.